Antibiotic sensitivity testing of anaerobic bacteria by the breakpoint method.

A shortened form of the agar dilution procedure (breakpoint method) was studied for susceptibility testing of 363 strains of anaerobic bacteria under routine conditions. Mezlocillin inhibited 99%, piperacillin 96%, cefoxitin 99%, latamoxef 90%, clindamycin 96% and metronidazole 100% of Bacteriodaceae strains tested. Peptococcaceae were susceptible to penicillins, cephalosporins and metronidazole. We did not find noticeable resistance of Clostridium perfringens strains to beta-lactam antibiotics or metronidazole, but to tetracycline and clindamycin. Propionibacteria were fully susceptible to beta-lactam antibiotics, tetracycline, erythromycin and clindamycin.